Scientists in California have developed a novel device that harnesses sun and sewage to produce hydrogen fuel, at the same time as improving the efficiency of wastewater treatment. The device is made up of two components: a microbial fuel cell (MFC) and a kind of solar cell called a photoelectrochemical cell (PEC). In the MFC component, bacteria degrade organic matter in the wastewater, generating electricity in the process. The biologically generated electricity is delivered to the PEC component to assist the solar-powered splitting of water (electrolysis) that generates hydrogen and oxygen.
Both types of fuel cells can produce electricity on their own but are expensive when used on a large scale as additional electricity is required. In comparison, the hybrid solar-microbial device is self-driven and self-sustained, because the combined energy from the organic matter (harvested by the MFC) and sunlight (captured by the PEC) is sufficient to drive electrolysis of water.
A press release from the University of California describes additional technical details. But I think the technique is worth circulating more widely, as hydrogen production is often criticised for being energy-intensive – and this looks like it won’t be.